A known problem which arises with such sprinklers, and in particular micro-sprinklers, whether these are of the rotary or of the static kind, is connected with the variation of output rate, spray range and distribution pattern as a consequence of variations in input pressure to the sprinkler, whether these arise as a result of variations in mains supply or as a result of variations in terrain which give rise to differing supply pressures reaching differing sprinklers.
In an attempt to overcome this particular problem, it has been known to associate the water supply to the sprinkler with suitable pressure or flow control means, by which it is desired to ensure that the water reaching the outlet nozzle of the sprinkler is always at a substantially constant outflow rate, irrespective of the supply pressure.
A further problem which arises is associated with sprinklers which are desired to operate at a relatively low output rate. Achieving such a relatively low output rate, and at the same time ensuring that the spray outflow is of sufficient velocity to ensure maintaining an adequate spray range, has involved the use of nozzles with increasingly smaller outflow apertures. It will be readily appreciated that the smaller the outflow aperture, the greater the danger that this aperture becomes blocked by grit and the like.
It is an object of the present invention to provide a new and improved irrigation sprinkler in which some or all of the above-referred-to disadvantages are significantly reduced.